1. Field of the Invention
The present invention relates to the fields of electronic circuit design and testing. In particular, the present invention relates to the automatic conversion of test pattern drawings of electrical circuits into test files which can be used as direct input to computer-aided design (CAD) tools or integrated circuit (IC) testing equipment.
2. Background of the Invention
Currently, the Department of Defense (DoD) maintains a large inventory of documentation for electronic systems. The existing documentation is in the form of circuit drawings, test pattern drawings, and associated information. Many of these documents have already been scanned and are stored as scanned image files. However, these files are only abstract representations of circuits, and as such cannot be directly used as input to computer-aided design (CAD) tools or integrated circuit (IC) testers. In order to re-specify or re-manufacture an electronic part, board, or system, a considerable amount of time and human effort must be expended to collect and understand the circuit information, such as inputs and outputs, from the circuit drawing. In order to ensure that the re-designed device is functioning correctly, the test pattern drawings, which specify the response to stimulus expected of electronic circuits, must also be converted into a form that can be used for simulation and IC testing.
The ability to re-specify and re-manufacture circuits is essential for DoD and industry to efficiently and automatically maintain and upgrade system electronics. This ability particularly affects those organizations concerned with building and maintaining fleets of high-cost, long-lived electronic-dependent systems facing the same problems associated with maintaining proper documentation, continuous upgrades, the obsolescence of commercial integrated circuit (IC) technology, and document storage and retrieval.
The term "test pattern drawing" is defined as a document, such as a test word truth table, specifying testing characteristics of a given circuit or component, rather than a drawing in the pictorial sense. For example, a typical test pattern drawing is composed of multiple pages where each page contains test pattern information and data arranged in a tabular format of rows and columns. This format is defined as the "test word truth table" drawing, and it is important to recognize that no schematic or drawing in the conventional pictorial sense is provided. These definitions apply in conjunction with any other commonly accepted definitions of these terms.
A test pattern drawing describes a properly functioning IC by listing the input patterns, or test words, supplied to the IC being tested and the corresponding output patterns. Other relevant information, including the pin names and/or pin numbers, test line numbers, and whether or not the output is to be tested is also typically included in the drawing. The information contained in a test pattern drawing is only intelligible to a trained human observer who first interprets the information content of the drawing based on specialized knowledge and experience and then manually enters the test pattern information as needed in CAD tools or IC testers.
A complete set of test patterns, even for a simple device, will generally consist of a number of drawing pages. The drawing set for test patterns alone can become especially large for complicated devices which typically require over 250,000 test vectors. Therefore, the productivity improvement in automating this manual process for circuit and board re-design and re-engineering is particularly significant.
Until now there has been no cost-effective, automatic way to convert the test information from the "test word truth table" of a test pattern drawing into a machine-readable data file format. There has been no method that accurately reproduces the necessary input and output information in CAD format to readily replicate the equipment's test parameters without human intervention.
Therefore, there is a long-felt need in the art to automatically convert test pattern data from a "test word truth table" into a machine-readable format, such as a specially formatted text file. Such a file can be used by a CAD tool to provide input stimulus to a simulation model to check the model's responses and verify that the model is providing the correct outputs. Similarly, such a machine-readable file can be used by IC testing equipment to generate input stimuli to the IC's input pins and to check the output observed at the IC's output pins to verify that the physical device is functioning properly. The present invention addresses this need for efficient and cost-effective methods suitable for use with CAD technology.